Ch. 29] GENERAL SURVEY OF REPLACEMENT DEPOSITS 



529 



Some Major Replacement Deposits 



In Non-sedimentary Rocks 

 Pre-Cambrian iron ores, Missouri 

 Tennessee copper (Ducktown) 

 Appalachian and Adirondack magne- 

 tites 

 Buchans, N. F., copper-lead-zinc 

 Ontario-Quebec copper-gold-zinc re- 

 placements (Noranda, etc.) 

 Also Manitoba copper-zinc (Hudson 



Bay, etc.) 

 Sudbury, Ontario, nickel-copper 

 Michigan copper (in lavas) 

 Cerro de Pasco area, Peru (in part) 

 Burma, lead-zinc (Bawdwin) 

 All porphyry coppers of western U. S. 

 (Bingham, Utah; Santa Rita, N. M.; 

 Ajo, Ariz., etc.) 



In Sedimentary Rocks 



Mississippi Valley deposits (S.E. Mis- 

 souri, lead; Joplin region, lead-zinc; 

 Wisconsin-Illinois, lead-zinc) 



Appalachian zinc deposits (East Ten- 

 nessee; S.W. Virginia; Friedensville, 

 Pa.) 



Pre-Cambrian limestone replacements, 

 eastern U. S. and Canada (Franklin, 

 N. J., zinc; Edwards-Balmat, N. Y., 

 zinc; eastern Ontario and Quebec, 

 lead-zinc replacements) 



Michigan copper (in conglomerates) 



Sullivan Mine, B. C, lead-zinc 



Kennecott, Alaska, copper 



Metaline Falls, Wash., lead-zinc 



Leadville, Colo., lead-zinc 



Utah lead-zinc, in part (Park City, etc.) 



Central New Mexico, lead-zinc 



Mexican manto deposits (lead-zinc in 

 limestone) 



Aguilar, Argentina, lead-zinc 



Broken Hill and Mt. Isa, Australia, 

 lead-zinc 



Silesian lead-zinc 



Rhodesian copper deposits 



Rio Tinto, Spain, copper-pyrites 



Many pyritic replacements (Appala- 

 chians^ etc.) 



is more an example of cavity filling (solution cavities) than of actual 

 replacement, but the cavities are generally regarded as a result of the 

 processes by which ore deposits were emplaced in a particular forma- 

 tion. If these qualifications are accepted, our list covers the field of 

 important lead-zinc mines fairly well. 



Probably the most important second group, if it were detailed in 

 full, is the pyritic replacements, in part called fahlbands, which are 

 far more numerous than indicated but are apt to be ignored because 

 few of them can be exploited economically. Pyritic deposits can occur 

 in sedimentary rocks of normal facies (Missouri sinkhole fillings, etc.) 

 but are most typical in substantially metamorphosed rocks, very com- 

 monly of schistose or slaty character, as at Rio Tinto and in the Ap- 

 palachian region. 



More important economically, at present, are the enormous copper 

 sulphide replacements of Rhodesia and adjacent Central Africa. 



